This invention relates to the stabilization of organic material normally tending to deteriorate. In particular, the invention relates to the protection of synthetic polymers against the harmful degradative effects, such as discoloration and embrittlement caused by exposure to light, especially ultraviolet light.
It is known that actinic radiation, particularly in the near ultraviolet region, has a deleterious effect on both the appearance and properties of organic polymers. For example, normally colorless or light colored polyesters yellow on exposure to sunlight as do such cellulosics as cellulose acetate. Polystyrene discolors and cracks, with accompanying loss of its desirable physical properties when exposed to actinic light, while vinyl resins, such as polyvinyl chloride and polyvinyl acetate spot and degrade. The rate of air oxidation of polyolefins such as polyethylene and polypropylene is materially accelerated by ultraviolet light.
It has been proposed to stabilize polymeric materials against ultraviolet light deterioration by the use of various types of ultraviolet absorbers. Thus, U.S. Pat. No. 3,004,896 discloses for this purpose 2(2-hydroxyphenyl)benzotriazole derivatives, while U.S. Pat. No. 3,189,630 discloses certain metal salts of hydroxybenzoic acids which are useful as actinic stabilizers in synthetic polymers.
The present invention is directed to a class of ultraviolet light stabilizers which consist of a compound of the formula ##EQU1## wherein R.sup.1 and R.sup.2 are independently of each other methyl or ethyl or together with the carbon to which they are bound form a cyclopentyl or cyclohexyl ring, which is unsubstituted or substituted with a methyl group;
n is an integer of from 1 to 2; PA1 When n is 1, R.sup.3 is an alkyl group of from 1 to 20 carbon atoms; PA1 When n is 2, R.sup.3 is an alkylene group of from 2 to 8 carbon atoms; and PA1 D is alkyl group having from 6 - 12 carbon atoms or --(C.sub.w H.sub.2w)--S--R"
A is a straight or branched chained (lower)alkylene group containing from 1 to 6 carbon atoms with the limitation that the terminals of said alkylene group bear only hydrogen or one (lower)alkyl group.
By the term alkyl as represented by R.sup.1 and R.sup.2 is intended methyl or ethyl, with methyl being the preferred substituent. Representative of the cycloalkyl groups, as represented by R.sup.1 and R.sup.2, are cyclohexyl, cyclopentyl, 2-methyl, 3-methyl and 4-methylcyclohexyl, and 2-methyl and 3-methylcyclopentyl. The preferred cycloalkyl groups are cyclohexyl and 2-methylcyclohexyl.
Illustrative examples of the (lower)alkylene groups as represented by A are methylene, ethylene, 1,2-propylene, n-propylene, 2,3-propylene, ethylidene, triethylene, 1,4-tetramethylene, 1-methyl-1,3-trimethylene, 2-methyl-1,3-trimethylene, pentamethylene, hexamethylene and the like.
This invention also relates to compositions of matter which are stabilized against ultraviolet light deterioration which comprises a synthetic organic polymer normally subject to ultraviolet deterioration containing from about 0.005% to 5% by weight of the polymer of the compounds of formula 1 and preferably from 0.01% to 2% by weight.
Alkyl alkanoate derivatives of the substituted piperazine diones as represented by formula I can be used in combination with other light stabilizers such as 2(2-hydroxyphenyl)benzotriazoles, 2-hydroxybenzophenones, nickel complexes and benzoates.
The stabilizers of this invention are suitable for the protection of many synthetic polymers from the deleterious effects of light. Homopolymers, copolymers, and mixtures thereof are embraced within the scope of substrates which may be stabilized with the stabilizers of this invention, along which may be mentioned, polystyrene and including homopolystyrene and copolymers with acrylonitrile and/or butadiene; vinyl resins formed from the polymerization of vinyl halides or from copolymerization of vinyl halides with unsaturated polymerizable compounds, for example, vinyl esters, .alpha.,.beta.-unsaturated acids, .alpha.,.beta.-unsaturated esters, and unsaturated hydrocarbons such as butadienes and styrene; poly-.alpha.-olefins such as high and low density polyethylene, cross-linked polyethylene, polypropylene, poly(4-methyl-pentene-1) polybutene-1, and the like including copolymers of poly-.alpha.-olefins such as ethylene-propylene copolymers, and the like; polybutadiene; polyisoprene; polyurethanes such as are prepared from polyols and organic polyisocyanate; polyamides such as hexamethylene-adipamide; polyesters such as polymethyleneterephthalates; polycarbonates such as those prepared from bisphenol-A and phosgene; polyacetals; polyethylene oxide; and polyacrylics such as polyacrylonitrile; polyphenyleneoxides such as those prepared from 2,6-dimethylphenol and the like. Particularly preferred polymers for the compositions of this invention are those normally solid polymers of alpha-olefins having up to 3 carbon atoms, e.g., ethylene-propylene and their copolymers.
The stabilized polymers of the present invention have utility in the normal uses for which plastics are employed and particularly useful for film and fiber. Compounds of this invention may be incorporated in the polymeric substance during the usual processing operations, for example, by hot milling, the composition then being extruded, pressed. blow molded or the like into films, fibers, filaments, hollow spheres and the like. Where the polymer is prepared from a liquid monomer as in the case of styrene, the stabilizer may be dispersed or dissolved in the monomer prior to polymerization or curing.
In addition to the actinic stabilizers described, the plastic compositions may contain other additives such as plasticizers, pigments, fillers, dyes, glass or other fibers, thermal antioxidants, and the like. For example in most applications, it is desirable to incorporate into the resin composition, sufficient thermal antioxidants to protect the plastic against thermal and oxidative degradation. The amount of antioxidant required will be comparable to that of the actinic stabilizer. Namely, from about 0.005% to 5% and preferably from 0.01% to 2% by weight. Representative of such antioxidants are phosphite esters, such as triphenylphosphite and dibutylphosphite and alkyl arylphosphites such as dibutylphenylphosphite, and the like.
The best results are obtained with the preferred class of thermal antioxidants, the hindered phenols. These compounds have been found to provide the best thermal stabilization with the least discoloration in the compositions of the invention. Typical of these phenolic antioxidants include the following:
1. Phenolic compounds having the general formula EQU Q--(CH.sub.2).sub.w --A
wherein
Q is ##SPC1##
A is -- CR(COOR").sub.2 ##EQU2##
R is hydrogen or lower alkyl
R' is lower alkyl
R" is alkyl group having from 6 - 24 carbon atoms
w is an integer from 0 to 4.
Illustrative examples of the compounds shown above are
di-n-octadecyl .alpha. (3,5-di-t-butyl-4-hydroxybenzyl)malonate
di-n-octadecyl .alpha.-(3-t-butyl-4-hydroxy-5-methyl-benzyl)malonate which is disclosed in the Netherlands Pat. No. 6,711,199, February 19, 1968
di-n-octadecyl-.alpha.,.alpha.'bis-(3-t-butyl-4-hydroxy-5-methylbenzyl)malo nate which is disclosed in the Netherlands Pat. No. 6,803,498, Sept. 18, 1968.
2. Phenolic compounds having the general formula EQU Q--R
illustrative examples of the compounds shown above are
2,6-di-t-butyl-p-cresol
2-methyl-4,6-di-t-butylphenol and the like.
3. Phenolic compounds having the formula EQU Q--C.sub.w H.sub.2w --Q
2,2'-methylene-bis(6-t-butyl-4-methylphenol)
2,2'-methylene-bis(6-t-butyl-4-ethylphenol)
4,4'-butylidene-bis(2,6-di-t-butylphenol)
4,4'-(2-butylidene)-bis-(2-t-butyl-5-methylphenol)
2,2'-methylene-bis[6-(1-methylcyclohexyl)-4-methylphenol
and the like.
4. Phenolic compounds having the formula EQU R--O--Q
illustrative examples of such compounds are 2,5-di-t-butylhydroquinone
2,6-di-t-butylhydroquinone
2,5-di-t-butyl-4-hydroxyanisole
5. Phenolic compounds having the formula EQU Q--S--Q
Illustrative examples of such compounds are
4,4'-thiobis-(2-t-butyl-5-methylphenol)
4,4'-thiobis-(2-t-butyl-6-methylphenol)
2,2'-thiobis-(6-t-butyl-4-methylphenol)
6. Phenolic compounds having the formula ##EQU3##
Illustrative examples of such compounds are octadecyl-(3,5-dimethyl-4-hydroxybenzylthio)-acetate
dodecyl-(3,5-di-t-butyl-4-hydroxybenzylthio)-propionate
7. Phenolic compounds having the formula ##EQU4## wherein T is hydrogen
R or Q as defined above.
Illustrative examples of such compounds are
1,1,3-tris(3,5-dimethyl-4-hydroxyphenyl)-propane
1,1,3-tris(5-t-butyl-4-hydroxy-2-methylphenyl)-butane
1,1,5,5-tetrakis-(3'-t-butyl-4'-hydroxy-6'-methylphenyl)-n-pentane
8. Phenolic compounds having the formula ##SPC2##
wherein B.sup.1, B.sup.2 and B.sup.3 are hydrogen, methyl or Q, provided that when B.sup.1 and B.sup.3 are Q then B.sup.2 is hydrogen or methyl and when B.sup.2 is Q then B.sup.1 and B.sup.3 are hydrogen or methyl.
Illustrative examples of such compounds are
1,4-di(3,5-di-t-butyl-4-hydroxybenzyl)-2,3,5,6-tetramethylbenzene
1,3,5-tri(3,5-di-t-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene
9. Phenolic compounds having the formula ##EQU5##
wherein Z is NHQ, --S--D or --O--Q
Illustrative examples of such compounds are
2,4-bis-(n-octylthio)-6-(3,5-di-t-butyl-4-hydroxyaniline)-1,3,5-triazine
6-(4-hydroxy-3-methyl-5-t-butylanilino)-2,4-bis-(n-octylthio)-1,3,5-triazin e
6-(4-hydroxy-3,5-dimethylanilino)-2,4-bis-(n-octylthio)-1,3,5-triazine
6-(4-hydroxy-3,5-di-t-butylanilino)-2,4-bis-(n-octylthioethylthio)-1,3,5-tr iazine
6-(4-hydroxy-3,5-di-t-butylanilino)-4-(4-hydroxy-3,5-di-t-butylphenoxy)-2-( n-octylthio)-1,3,5-triazine
2,4-bis(4-hydroxy-3,5-di-t-butylanilino)-6-(n-octylthio)-1,3,5-triazine.
The above phenolic triazine stabilizers are more fully described in U.S. Pat. No. 3,255,191.
10. Phenolic compounds having the formula ##EQU6##
wherein Z' is --O--Q, --S--D or --S--(C.sub.w H.sub.2w)--SD
Illustrative examples of such compounds are
2,3-bis-(3,5-di-t-butyl-4-hydroxyphenoxy)-6-(n-octylthio)-1,3,5-triazine
2,4,6-tris-(4-hydroxy-3,5-di-t-butylphenoxy)-1,3,5-triazine.
6-(4-hydroxy-3,5-di-t-butylphenoxy)-2,4-bis-(n-octylthioethylthio)-1,3,5-tr iazine
6-(4-hydroxy-3-methylphenoxy)-2,4-bis-(n-octylthio)-1,3,5-triazine
6-(4-hydroxy-3-t-butylphenoxy)-2,4-bis-(n-octylthioethylthio)-1,3,5-triazin e
6-(4-hydroxy-3-methyl-5-t-butylphenoxy)-2,4-bis-(n-octylthio)-1,3,5-triazin e
2,4-bis-(4-hydroxy-3-methyl-5-t-butylphenoxy)-6-(n-octylthio)-1,3,5-triazin e
2,4,6-tris-(4-hydroxy-3-methyl-5-t-butylphenoxy)-1,3,5-triazine
6-(4-hydroxy-3,5-di-t-butylphenoxy)-2,4-bis-(n-octylthiopropylthio)-1,3,5-t riazine
6-(4-hydroxy-3,5-di-t-butylphenoxy)-2,4-bis-(n-dodecylthioethylthio)-1,3,5- triazine
2,4-bis-(4-hydroxy-3,5-di-t-butylphenoxy)-6-butylthio-1,3,5-triazine
2,4-bis-(4-hydroxy-3,5-di-t-butylphenoxy)-6-(n-octadecylthio)-1,3,5-triazin e
2,4-bis-(4-hydroxy-3,5-di-t-butylphenoxy)-6-(n-dodecylthio)-1,3,5-triazine
2,4-bis-(4-hydroxy-3,5-di-t-butylphenoxy)-6-(n-octylthiopropylthio)-1,3,5-t riazine
2,4-bis-(4-hydroxy-3,5-di-t-butylphenoxy)-6-(n-octylthioethylthio)-1,3,5-tr iazine
2,4-bis-(4-hydroxy-3,5-di-t-butylphenoxy)-6-(n-dodecylthioethylthio)-1,3,5- triazine.
The above phenolic triazine stabilizers are more fully described in U.S. Pat. No. 3,255,191.
11. Phenolic compounds having the formula ##EQU7##
wherein p is an integer from 2 to 4 and
R'" is a tetravalent radical selected from aliphatic hydrocarbons having from 1 to 30 carbon atoms
aliphatic mono and dithioethers having from 1 to 30 carbon atoms
aliphatic mono and diethers having from 1 to 30 carbon atoms and
z is an integer from 0 to 6.
Illustrative examples of such compounds are